1. Field of the Invention
Exemplary embodiments of the present invention relate to a method of fabricating a light emitting diode (LED), and more particularly, to a method of fabricating an LED having improved crystal quality.
2. Discussion of the Background
In general, gallium nitride (GaN)-based semiconductors are widely used for ultraviolet (UV) or blue/green light emitting diodes or laser diodes as light sources of full-color displays, traffic lights, general illuminators, and optical communication devices. Such a GaN-based light emitting device may have an InGaN-based active layer of a multiple quantum well structure, which is interposed between an n-type GaN semiconductor layer and a p-type GaN semiconductor layer, and emits light through recombination of electrons and holes in the active layer.
The n-type GaN semiconductor layer may be doped with silicon (Si) impurities, and the p-type GaN semiconductor layer may be doped with magnesium (Mg) impurities. Manufacturing process parameters of a GaN semiconductor layer, such as a total flow rate, a flow rate of source gas, a ratio of metal source gas and nitrogen gas, a growth temperature, and the like, may be selected depending on the composition of the GaN semiconductor layer, the kind of doping impurity, the kind of layer on which the GaN semiconductor layer is grown, and the like.
In a case where a high voltage such as static electricity is applied to an LED, the high voltage may damage the LED, and therefore, it may be necessary to ensure resistance against static electricity or the like. Particularly, in order to enhance the resistance of the LED against static electricity or the like, a leakage current may be reduced in the LED by improving the crystal quality of GaN-based semiconductor layers.
FIG. 1 shows a temperature profile of a method of fabricating an LED using a metal oxide chemical vapor deposition (MOCVD) method.
Referring to FIG. 1, an n-type GaN-based compound semiconductor layer is grown on a substrate at a temperature T1 of the substrate. During this time, a metal (e.g., Ga, Al or In) source gas, a nitride source gas, and a carrier gas are supplied onto the substrate. When the growth of the n-type GaN-based compound semiconductor layer is completed, the supply of the metal source gas is stopped, the temperature of the substrate is decreased to T2, and an active layer is grown on the n-type GaN-based compound semiconductor layer. After the growth of the active layer is completed, the supply of the metal source gas used to grow the active layer is stopped, the temperature of the substrate is increased from T2 to T3, and a p-type GaN-based compound semiconductor layer is grown on the active layer at T3. Here, a metal-organic material may be used as a raw material of the metal source gas, and NH3 is used as the nitride source gas.
According to the conventional method, each GaN-based compound semiconductor layer may be grown at a suitable growth temperature and flow rate conditions. However, the LED fabricated using the aforementioned method may have a relatively high leakage current, and the LED may require a zener diode due to a low resistance against static electricity.